Issue Archive

Dr. Bruce Wielicki, senior Earth scientist within the
Science Directorate at Langley Research Center, works as lead of the Climate
Absolute Radiance and Refractivity Observatory (CLARREO) mission. The Tier-1
earth science decadal survey initiative will anchor a future climate observing
system.

NASA Tech Briefs: What is the CLARREO
mission?

Dr. Bruce
Wielicki: CLARREO is a mission to take us into a new level of accuracy of
instruments in orbit. CLARREO takes some of these high-accuracy infrared and
reflected solar capabilities that we’ve built in the laboratories and some of
the NASA research centers, and gets them up into orbit — seeing the whole Earth, so
that we can get really accurate climate change data about where the planet is
going. There’s a lot of discussion and arguments about how accurate different
data sources are. Instead of targeting accuracy the way we normally do for
instantaneous weather measurements, the mission targets that accuracy at
decadal change measurements, and those are typically required at almost a
factor of 5 or 10 more accurate than weather observations are.

To give you an example: You might need a 1 Kelvin temperature
measurement to understand tomorrow’s weather. You need 1/10 of a Kelvin
accuracy to get decadal change, as we put greenhouse gases in the atmosphere
and have to watch how the planet is responding, and then make our changes
relative to that. So that is really CLARREO’s mission: to get that accuracy up
in orbit, and then also to do it across the whole spectrum of earth’s energy emitted
to space, because that’s what drives climate. So the reflected solar all the
way from the ultraviolet into the near infrared, the mid-infrared, and the
far-infrared. That far-infrared has never been observed from space, so that’s a
new and exciting part of this mission. It allows CLARREO to cover so much of
the spectrum so that we can become a standard radiometer in orbit to improve
the calibration of other instruments, including weather instruments or Landsat
instruments. We can actually match them in time-angle space, calibrate them
much more accurately to our standard, and bring the whole observing system up
in accuracy and capability.

NTB: How do these
tools ensure accurate results?

Dr. Wielicki: When
we build instruments normally, we’re trying to see the whole Earth at really
high resolutions — see down into pixels where we can get individual clouds,
for example, or landscapes for vegetation. [CLARREO] instruments are kind of
the opposite mode. We back off in things like spatial resolution to make them
simpler, but we hone in in terms of really high accuracy. We’ll have special
black bodies — a black body is a deep cavity where you can control very
accurately the temperature that the instrument observes, and then know that
temperature with accuracy that is down to hundredths of a degree. We reach the temperature accuracy by using
phase-change cells. These small cells mounted in the black body allow you to
change different materials from solid to liquid, and thereby know exactly where
those temperatures are, and then use those across ranges of temperature to
determine the temperatures your instrument can sense. We can’t afford to do
that kind of accuracy on most of our weather and other instruments, so what we
have to go for here is a really different shot of how to do that.

NTB: Where does
the CLARREO mission stand currently, and how have budget cuts changed the
plans?

Dr. Wielicki: That’s
been the bad news for us. The science itself has been extraordinary, and we’ve
spent about three years really well determining the science requirements. We
have the climate modeling community involved, so we’re actually simulating the
CLARREO observations in climate models. We can actually show over 100 years in
model simulation what CLARREO would have seen, and what it could have told us
about climate change.

Just as we were ready to knock on the door that was going
to start this mission formally, that’s when the budget cuts to NASA’s science
program came. So we’re now on indefinite hold, and instead of having a launch
date in 2017 or 2018, we’re now kind of idling. Instead of marching toward a
mission date, what we’re doing is continuing to extend the accuracy of the
climate studies, in particular these climate models, and retire some of the
risks in technology.

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